The invention relates to a method and apparatus for establishing a negative pressure inside an enclosure that houses a fuel cell system.
A fuel cell is an electrochemical device that converts chemical energy that is produced by a reaction directly into electrical energy. For example, one type of fuel cell includes a proton exchange membrane (PEM), often called a polymer electrolyte membrane, that permits only protons to pass between an anode and a cathode of the fuel cell. At the anode, diatomic hydrogen (a fuel) is reacted to produce hydrogen protons that pass through the PEM. The electrons produced by this reaction travel through circuitry that is external to the fuel cell to form an electrical current. At the cathode, oxygen is reduced and reacts with the hydrogen protons to form water. The anodic and cathodic reactions are described by the following equations:
H2xe2x86x922H++2exe2x88x92at the anode of the cell, and
O2+4H++4exe2x88x92xe2x86x922H2O at the cathode of the cell.
Because a single fuel cell typically produces a relatively small voltage (around 1 volt, for example), several fuel cells may be formed out of an arrangement called a fuel cell stack to produce a higher voltage. The fuel cell stack may include plates (graphite composite or metal plates, as examples) that are stacked one on top of the other, and each plate may be associated with more than one fuel cell of the stack. The plates may include various channels and orifices to, as examples, route the reactants and products through the fuel cell stack. Several PEMs (each one being associated with a particular fuel cell) may be dispersed throughout the stack between the anodes and cathodes of the different fuel cells.
The fuel cell stack typically is housed in an enclosure that encloses the stack and other components of a fuel cell system. In some cases, the fuel cell system may leak small amounts of gases, such as hydrogen, for example. For purposes of maintaining safe operation of the fuel cell system, a blower may be located inside the enclosure to establish a positive pressure inside the enclosure to both dilute any stray gases and force the diluted gases outside of the enclosure. Because the stray gases must be diluted to a very small concentration outside of the enclosure, typically the blower must generate a large air flow, an air flow that might freeze compartments of the fuel cell system.
Thus, there is a continuing need for an arrangement that addresses one or more of the problems that are stated above.
In an embodiment of the invention, a fuel cell system includes a fuel cell stack, an enclosure housing the fuel cell stack and a blower that is located inside the enclosure. The blower is adapted to draw air from an interior of the enclosure to produce an air flow through the fuel cell stack and establish a negative pressure inside the enclosure with respect to a region outside of the enclosure.